Halogen type tungsten filament lamp including ammonium in its gas fill

ABSTRACT

A halogen bulb having a tungsten filament and containing a reactive carrier gas mixture including halogen, as well as an inert gas in a transparent envelope to repeatedly regenerate tungsten evaporated from the filament during operation. Improvement lies in using hydrogen bromide and ammonium bromide as the reactive carrier gas mixture, thereby providing a bulb of high efficiency, and uniformly long service life.

United States Patent Inventor Kenlchi Konishi Kyoto, Japan Appl. No. 758,700 Filed Sept. 10, 1968 Patented June 8, 1971 Assignee Matsushita Electronics Corporation Kadoma-shi, Osaka, Japan Priority Sept. 12, 1967 Japan 42/58960 HALOGEN TYPE TUNGSTEN FILAMENT LAMP INCLUDING AMMONIUM IN ITS GAS FILL 5 Claims, No Drawings [56] References Cited UNITED STATES PATENTS 3,09 l ,7 l 8 5/1963 Shurgan 313/222 3,277,330 l0/l966 Cooper, Jr..... 3l3/222X 3,311,777 3/l967 Schroder 313/222X 3,418,512 I2/l968 TJampens et al. 3 l3/222X Primary Examiner- Roy Lake Assistant Examiner- Palmer C. Demeo Attorney-Stevens, Davis, Miller and Mosher ABSTRACT: A halogen bulb having a tungsten filament and HALOGEN TYPE TUNGSTEN FILAMENT LAMP INCLUDING AMMONIUM IN ITS GAS FILL This invention relates to a halogen bulb (a bulb containing halogen gas) and more particularly to an incandescent halogen lamp having a tungsten filament and containing a reactive carrier gas as well as an inert gas, said carrier gas performing a regeneration cycle by converting tungsten evaporated from the filament during operation into a volatile compound and decomposing the compound near or on the filament to regenerate tungsten, thereby preventing blackening of the envelope.

It is well known that by sealing in a quartz tube a minute quantity of such halogenous gas as iodine or bromine in the form of an element or a compound and by maintaining the wall of the quartz tube and the filament at appropriate temperatures, a regeneration cycle of tungsten is achieved through such halogenous gas existing in the space between the filament and the tube wall.

Halogen lamps have such features that the blackening of the bulb is prevented throughout its service life by means of the regeneration cycle mentioned above, and that the evaporation of the tungsten filament is suppressed by using an envelope of small dimensions and filling an inert gas at a high pressure, thereby making its service life notably long as compared with general incandescent electric lamps.

Of halogen lamps, an iodine lamp wherein iodine sealed therein is made use of as a carrier which plays the main role in the regeneration cycle has been brought into practice. Although such iodine lamp is advantageous in that it enjoys a long service life without blackening of the envelope throughout the service life, it has considerable disadvantages, namely the following. The manufacture of iodine lamps requires complex processes in comparison to those of the conventional incandescent electric lamps, and the irregularity of quality due to the variation in the manufacturing conditions is considerably large. For this reason, a strict control of manu facturing conditions is inevitable with the accompanying difficulties in their process of manufacturing. Furthermore, because iodine gas sealed in the quartz envelope has a property of absorbing some amount of light rays, a decrease in efficiency is inevitable.

To eliminate such deficiencies, the use of hydrogen bromide or such an alkyl bromide compounds as methylene bromide (CH Br which generates hydrogen bromide (HBr) upon decomposition is proposed in place of iodine. Such methylene bromide decomposes and generates hydrogen bromide on the surface or in the neighborhood of the filament kept at a high temperature during operation, and the regeneration cycle is carried out through such generated hydrogen bromide. Such halogen lamps that contain hydrogen bromide or alkyl bromide compounds are quite excellent for electric lamps of high color temperature and short service life or for electric lamps subjected to repetitive switching. However, such halogen lamps of longer service life have considerable irregularities in their service lives. The reason for this phenomenon is considered to be as follows.

When methylene bromide is sealed in the quartz envelope together with an inert gas, methylene bromide partially decomposes and generates chemically active hydrogen bromide. Furthermore, during the service life of the lamp, hydrogen generated by the decomposition of hydrogen bromide is gradually lost and bromine which is more active than hydrogen bromide is left. On account of this fact, the quantity of carrier gas, i.e. methylene bromide, to be sealed in, should be strictly limited for those halogen lamps of low color temperature and long service life. Accordingly, due to inevitable variations in the filling pressure in the manufacturing process, the amount of the carrier gas, i.e. methylene bromide, sealed with an inert gas fluctuates. This fluctuation gives a great influence on the service life of the lamps. By reducing the amount of the carrier gas to be sealed in, such a problem as described above may be solved to some extent. But there occurs another problem namely that the amount of carrier gas becomes often insufficient and makes regeneration insufficient, whereby the blackening of the envelope occurs and the service life of the bulb is shortened. Considering these problems, there could be found no other way than to use iodine as the carrier gas for halogen lamps of longer service life than 2000 hours.

The object of this invention is to provide an electric lamps containing a reactive carrier gas which absorbs few light rays, wherein corrosion of tungsten at lower temperature portions rarely occurs, whereby a uniformly long service life is enjoyed with a high efficiency regardless of fluctuations in amounts of impurities and the carrier gas contained in the envelope.

According to this invention, a tungsten filament is encased in a transparent envelope which is heated to at least 300 C. during operation and a reactive carrier gas composed of hydrogen bromide and ammonium bromide is sealed in as well as an inert gas. Hydrogen bromide may partially decompose in the envelope into bromine and hydrogen. There may be more hydrogen contained than bromine.

The amount of bromine contained in the envelope in the form of element or hydrogen bromide is preferably at a value between l.5 10 and 1.05 l0 gram-atoms per 1 cc. the amount of ammonium-bromide is preferably in the range from one-tenth to 10 times of hydrogen bromide. When this ratio is smaller than 0.1, i.e. ammonium bromide is extremely small, a good result could not be obtained. When the ratio is larger than 10, the regeneration cycle becomes insufficient.

Hydrogen bromide and ammonium bromide may be sealed in the envelope as themselves. In this case, however, since ammonium bromide is in solid phase at ordinary temperatures, it must be introduced into the envelope after exhaustion by heating an ammonium bromide storage connected to the envelope in such a way that the vacuum system is kept at such a temperature that the vapor pressure of ammonium bromide coincides with the desired pressure.

Therefore, it is convenient to introduce hydrogen bromide and ammonium bromide into the envelope in the form of methylene bromide (CH Br and ammonia (NH;,). They may be introduced either separately or as a gas mixture wherein they are mixed in a predetermined ratio with an inert gas such as argon. Methylene bromide decomposes according to the following equation:

Carbon atoms generated react with oxygen remaining in the envelope, as a kind of getter. A part of hydrogen bromide reacts with ammonia to produce ammonium bromide:

The inventor made a halogen lamp of 1000 w. output power, 220 v. input and 2000 hours rated life, according to this invention. In the manufacturing process after encasing the filament in the envelope, equal amounts of argon mixed with 0.4 percent methylene bromide and argon mixed with 0.32 percent ammonium are successively introduced until the pressure in the envelope becomes 5 atmospheres. Then, the gas mixture is heated by energizing the filament, and a carrier gas consisting of hydrogen bromide and ammonium bromide is obtained. Ammonium bromide obtained in this way is sometimes observed with the naked eyes as a thin white deposit on the inner wall surface at the tube ends, while the lamp is being turned off. In most instances, however, its existence is not recognizable.

The initial luminous light flux was measured to make a comparison between the inventive halogen lamp and halogen lamps of other types. The result was identical to the case where methylene bromide along is used as a carrier gas, but a 3-5 percent larger flux was observed than that of the case where iodine is used as a carrier gas. This difference is considered to rise from the difference in light loss due to absorption by the carrier gas.

Next, tests were conducted on service life, Electric lamps containing hydrogen bromide and ammonium bromide as a carrier gas showed a higher average service life with smaller irregularities than those containing only hydrogen bromide. Namely, in the case where argon containing 0.2 percent methylene bromide and 0.l6 percent of ammonia was sealed in at atmospheres, a little more than 30 percent of the products showed service lives shorter than 2000 hours, and a little less than 60 percent of the products showed service lives longer than 2300 hours. In contrast, in the case where argon containing 0.2 percent of methylene bromide but no ammonia was sealed in 'at 5 atmospheres a little less than 70 percent of the products showed service lives shorter than 2000 hours and a little more than 20 percent of the products showed service lives longer than 2300 hours.

Further, when argon gas including 0.12 percent of methylene bromide only-an amount to produce same amount of hydrogen bromide as that produced from 0.2 percent methylene bromide and 0.16 percent ammonia-was sealed in at 5 atmospheres, a little more than 30 percent of the products were blackened after use during 1000 l 500 hours. This fact proves that the service life of a halogen lamp is greatly influenced by the existence of ammonium bromide within the envelope rather than by the amount of hydrogen bromide contained. The reason for this fact is considered to be that the concentration of hydrogen bromide is substantially reduced by the existence of ammonium bromide and that ammonium bromide achieves some buffering function against the loss of hydrogen or hydrogen bromide during the service life of the lamp,

It was turned out by a further study conducted based on the above result that the mol ratio of ammonium bromide to that of hydrogen bromide which are to be sealed in the quartz envelope should be altered to some extent depending on the construction of the lamp and its rating. Specifically, considerations should be given to the dimensions, designed service life, filament temperature, length of the linear parts of the filament at the ends and tolerable variation in quality of the lamp. Generally, good results were obtained when the mol ratio of ammonium bromide to hydrogen bromide falls within the range from 0. l to 10. When the-mol ratio was smaller than 0.1, that is, the amount of ammonium bromide was too small relative to hydrogen bromide, the atmosphere within the tube is not sufficiently chemically active and a good result could not be obtained. On the other hand, when the mo] ratio was larger than 10, that is, ammonium bromide was too much relative to hydrogen bromide, the regeneration cycle did not work sufficiently. v

The above-mentioned range of mol ratio is especially effective to halogen lamps of longer service life. A halogen bulb according to this invention, which contains hydrogen bromide and ammonium bromide which are generated by decomposition after sealing has such advantages that the service life is greatly lengthened and at the same time great improvements are achieved in regard to extent of irregularity of service life and the blackening of bulbs that were inherent to conventional halogen lamps.

I claim:

1. A halogen bulb comprising a transparent envelope, a tungsten filament therein heatable to at least 300 C. during operation, an inert gas and a reactive carrier gas sealed therein, said reactive carrier gas consisting essentially of hydrogen bromide and ammonium bromide.

2. A halogen bulb according to claim 1, wherein the amount of bromine in the reactive carrier gas is in the range of 1.5 XlO'to l.05 l0'" 5 gram-atoms per 1 cubic centimeter.

3. A halogen bulb according to claim 1, wherein the mol ratio of ammonium bromide to hydrogen bromide is in the range of0.1 to 10. 1

4. A halogen bulb comprising a transparent envelope, a tungsten filament therein heatable to at least 300 C. during operation, an inert gas and a reactive carrier gas sealed therein, said reactive carrier gas consisting essentially of methylene bromide and ammonia.

5. A halogen bulb according to claim 4, wherein said envelope is filled with the equal amounts of argon mixed with 0.4 percent methylene bromide and argon mixed with 0.32 percent ammonium and its internal pressure is 5 atmospheres. 

2. A halogen bulb according to claim 1, wherein the amount of bromine in the reactive carrier gas is in the range of 1.5 107 to 1.05 X 10116 5 gram-atoms per 1 cubic centimeter.
 3. A halogen bulb according to claim 1, wherein the mol ratio of ammonium bromide to hydrogen bromide is in the range of 0.1 to
 10. 4. A halogen bulb comprising a transparent envelope, a tungsten filament therein heatable to at least 300* C. during operation, an inert gas and a reactive carrier gas sealed therein, said reactive carrier gas consisting essentially of methylene bromide and ammonia.
 5. A halogen bulb according to claim 4, wherein said envelope is filled with the equal amounts of argon mixed with 0.4 percent methylene bromide and argon mixed with 0.32 percent ammonium and its internal pressure is 5 atmospheres. 